1. Field of the Invention
The present invention relates to an apparatus for the maintenance of the needle-bearing plates which the needle-punching machines are equipped of.
2. Description of the Prior Art
As is known, in a needle-punching machine a compacted fiber web is repeatedly passed through, while it advances, by a multiplicity of barbed needles carried by a support or plate reciprocating in a direction perpendicular to the advancing direction. The repeated passage of the needles through the fiber web results in a close interlacing among the fibers giving mechanical stability to the workpiece.
Non-woven fabric, some types of wall-to-wall carpets and other types of products even in fields other than the textile one are usually produced with this technique.
The needle-bearing plates are generally made of aluminium and sometimes of wood and are formed with a multiplicity of seats arranged in a prefixed order where respective needles, generally made of steel, are engaged. The needles have at least a tapered portion starting from the pointed end, while the opposite end, the so called xe2x80x9cheelxe2x80x9d, is angle shaped and engage with a corresponding seat formed on a face of the plate.
The needle-bearing plates need a frequent maintenance for replacing both the bent or broken needles and those worn in correspondence of the end barbs which, due to the friction with the fibers, become rounded and therefore less effective.
Maintenance operation of the plates is presently carried out manually. Broken needles are found at sight, extracted and replaced. For the replacement of the worn needles a group replacement procedure is generally followed according to prefixed maintenance programs. In some cases, in which a group of needles is broken, broken needles are not replaced with new needles, but with used needles taken from random locations of the plate and these are replaced with new needles. In this way the risk of non-homogeneous works due to the presence of groups of needles with different degree of wear in different areas of the plate is avoided. Considering that the average size of the needle-bearing plates is 0.4xc3x972 m and that they carry 10,000 random arranged needles (approx.), it appears how hard these operations may be.
The object of the present invention is to provide an apparatus by means of which the maintenance operations of the needle-bearing plates can be carried out in a fully automatic way, thus making easier the task of the operators, reducing the maintenance time and improving the quality of the service.
A particular object of the present invention is to provide an apparatus of the above mentioned type by means of which each broken needle can be detected and extracted and a new needle inserted in the clear seat.
A further object of the present invention is to provide an apparatus of the above mentioned type by means of which a map of the plate can be initially created with memorisation of the position of each needle.
These objects are reached with the apparatus for the maintenance of the needle-bearing plates of a needle-punching machine according to the invention, comprising a bed on which there is mounted a frame supporting the needle-bearing plate to be submitted to maintenance and an operating head mobile with respect to said bed in two perpendicular directions defining a plane parallel to the liying plane of the plate mounted on the support frame. The operating head comprises:
means for extracting a damaged or worn needle comprising a pressing member alignable to the needle as a consequence of the movement of the operating head, mobile toward the needle for engaging the end portion thereof in such a way to exert a pushing action by means of the tapered portion thereof, and plier means for grasping the needle at the heel portion thereof to exert a traction force thereon, the plier means being frontally aligned to the pressing member and located at the opposite part with respect to the plate;
means for positioning a new needle in the respective seat of the plate comprising a needle inserting plier for taking the needle out of a new needle feeding device integrally mobile with the operating head, alignable to the seat as a consequence of a movement of the operating head and mobile toward said seat to provide for the partial insertion of the needle therewithin, and a pushing member located substantially sideways of the needle inserting plier, alignable to the partially inserted needle as a consequence of a movement of the operating head to engage the heel end portion of the needle and exert a pushing action capable of completing the insertion.
The apparatus further comprises a process control unit comprising a memory where a map of the seats of the needles present on the needle-bearing plate is stored, on the basis of which the movements of the operating head are controlled.
In a preferred embodiment the operating head also comprises means for detecting if a needle of the plate is broken or bent, sequentially alignable to each needle of the plate as a consequence of a movement of the operating head and mobile toward and from the needle to which they come into aligment.
Furthermore, in particular the apparatus comprises means for detecting the position of the seats for the needles formed on the plate on the basis of the actual position of the operating head and with respect to a reference position thereof, said detecting means comprising a detecting signal emitter and a receiver of said signal axially aligned and integral to the operating head, arranged at opposite parts with respect to the plate, the receiver generating a response signal once the detecting signal coming from the emitter passes through one of said seats, the response signal being processed by said process control unit to produce a seat map of the needles on said plate which is stored in the memory.
Further characteristics, as well as the advantages, of the apparatus for the maintenance of the needle-bearing plates mounted on a needle-punching machine according to the present invention will be apparent from the following description of an embodiment thereof, made as a non-limiting example with reference to the attached drawings.